How much will you pay?
and, do you already have the sim card and need the ID to register the sim, or do you need it to actually buy the sim? either way... Your new student I.D is 1234567891, $50 please.

For moderator sarcasm I won't pay anything.
I'm getting it off of ebay, I just need the info for registering the sim card and activating it.
$50 is a joke, if you're really serious send me a private message.

woo, harsh! I might be a little sarcastic but there was some truth in my post as well.
Most prepaid simcards and other sims you can get over the counter or off of ebay can be registered online
with very simply fake numbers.. a student number, medicare number, driver licence number etc can all be randomly made up on the registration form.. i have registered many simcards online with random numbers.. and i am not charging you anything for this advice. Give it a go and let us know how you go.

Side note, remember what details you do use, incase you ever need to ring up for support / recharge etc, anything involving having to talk to the company you got the sim from, they will often ask! record name, DOB, id used etc. enjoy!

well I found out lebara won't roam, so that's out.
i've narrowed it down to optus, telstra, amaysim, or vodaphone.

optus:
To activate your SIM, you'll need some ID. Any one of the following will get you going:
Medicare Card
Australian Driver's Licence
Australian Passport
Foreign Passport holding a valid Australian Visa (affixed visa label or electronic visa)
If you have an Optus My Account profile, log in here and we will check if your service is eligible to confirm your identification.

vodaphone:
A valid form of ID
For example: an Australian drivers licence, passport or Medicare card

telstra:
A valid form of ID
Australian Driver's Licence or Learner's Permit
Medicare card
Australian passport
International passport with valid Australian visa
ID image
If you're registered for My Account and receive a Telstra bill, you won't need an ID check to activate your Pre-Paid service. Otherwise, you'll need a form of ID that can be checked against a government database. Find out more. If you don't have any of the above IDs, see more options on how to activate.

Personally, i have used Virgin, Optus and Telstra... all with made up info, they have all worked.
Telstra is one of the main Carriers in Australia so i would say to avoid them, Optus and Virgin (virgin uses the optus network anyway) both have pretty good coverage.. i live in Rural Australia and optus/virgin works fine here but there is no Vodaphone towers anywhere nearby.

I have always found Virgin to be the easiest, optus should be about the same, i hope this helps!